Enhancing photocatalytic activity of tantalum nitride by rational suppression of bulk, interface and surface charge recombination

Rational design of photocatalysts is essential to achieve efficient solar energy conversion. For narrow bandgap Ta₃N₅ photocatalyst, various charge recombination occurring in the bulk, interface and on the surface significantly impairs its activity for solar hydrogen (H₂) generation. Herein, a synergistic engineering approach is designed to solve this critical recombination challenge. First, hollow spherical structure of Ta₃N₅ with Mg doping is prepared to not only reduce the charge migration distance and increase the surface area, but also increase the electron mobility for facilitated charge transfer. Second, an MgO nano-layer covers the surface of hollow Ta₃N₅ structure to passivate surface defects, thus promoting the interfacial charge transfer between Ta₃N₅ and co-catalysts. Finally, dual co-catalysts (Pt/CoO_x) for redox reactions are loaded onto the hollow Ta₃N₅ structure to reduce the surface recombination and overcome the sluggish surface reaction. Remarkably, the combination of hollow structure, Mg²⁺ doping, MgO interfacial layer, and dual co-catalysts effectively improves the charge separation and transfer in Ta₃N₅ photocatalyst. This newly designed photocatalyst exhibits a considerably improved H₂ generation performance of 56.3 μmol h⁻¹ under simulated sunlight, compared to that of reference Pt/Ta₃N₅ hollow spheres.